In residential and commercial construction, it is common to employ a drywall edge-trimming strip (corner bead) to trim a corner where two drywall panels approximate each other at a right angle or at an obtuse angle. Commonly, such a trimming is made from a suitable polymer, such as polyvinyl chloride. Commonly, such a trimming strip has a central portion having two lateral edges and two flanged portions, each of which extends from one of the lateral edges of the central portion.
If the drywall edge-trimming strip has a bullnose profile, each of the inner and outer surfaces of the central portion of the drywall edge-trimming strip has an arcuate profile. If the drywall edge-trimming strip has a mitered profile, each of the inner and outer surfaces of the central portion of the drywall edge-trimming strip is planar. Such drywall edge-trimming strips, which are extruded from polyvinyl chloride, are available commercially from Trim-Tex, Inc. of Lincolnwood, Ill., under its TRIM-TEX trademark.
Commonly, such drywall edge-trimming strips are assembled with two-legged (two-way) drywall corner-trimming devices and with three-legged (three-way) drywall corner-trimming devices, as exemplified in U.S. Pat. No. Re. 34,547, in U.S. Pat. No. 5,138,810, and, in a novel design, in U.S. Design Pat. application Ser. No. 29/093,817, supra. As exemplified in U.S. Pat. No. Re. 34,547, it is known for each leg of such a corner to have a projecting tab (tongue) which is adapted to fit under an end portion of a drywall edge-trimming strip. Such drywall corner-trimming devices, which are molded from acrylonitrile-butadiene-styrene, are available commercially from Trim-Tex, Inc. of Lincolnwood, Ill., under its TRIM-TEX trademark.
A problem that can occur with such a strip and with such a corner is "butt-edge separation", which refers to separation that can occur at the ends where two such strips approximate each other or where such a strip and one leg of such a corner approximate each other, and which can lead to unsightly conditions, such as cracked paint. In U.S. Pat. No. 5,740,642 and U.S. Pat. No. 5,813,179, the disclosures of which are incorporated herein by reference, the problem of butt-edge separation is addressed by splices. As disclosed in U.S. Pat. No. 5,740,642, a splice is stressed so as to be mechanically secured, although the splice also may be adhesively secured. As disclosed in U.S. Pat. No. 5,813,179, a splice is perforated so as to ventilate an adhesive layer securing the splice. As also disclosed in U.S. Pat. No. 5,813,179, suitable adhesives include construction adhesives of a type exemplified by MIRACLE DSA-20 adhesive available commercially from Miracle Adhesives Corporation of Newark, N.J., and by LIQUID NAILS adhesive available commercially from Macco Adhesives of Cleveland, Ohio.
If a drywall edge-trimming strip extruded from polyvinyl chloride is assembled with a drywall corner-trimming device molded from acrylonitrile-butadiene-styrene, and if an adhesive of the type discussed in the preceding paragraph or an adhesive of a type known as a "mirror mastic" and available commercially from various sources is used to secure the projecting tab (tongue) of the drywall corner-trimming device to and under one end portion of the drywall edge-trimming strip, the adhesive tends to adhere comparatively more strongly to a unit of surface area of the inner surface of the end portion of the drywall corner-trimming device and to adhere comparatively less strongly to a unit of surface area of the outer surface of the projecting tab (tongue) of the drywall corner-trimming device. Apparently, it is characteristic of such adhesives to adhere comparatively less strongly to a styrene polymer, such as acrylonitrile-butadiene-styrene, and to adhere comparatively more strongly to polyvinyl chloride.